|Steneck, Robert S.||University of Maine (U Maine DMC)||Principal Investigator|
|Estes, James||University of California-Santa Cruz (UC Santa Cruz)||Co-Principal Investigator|
|Rasher, Douglas B.||Bigelow Laboratory for Ocean Sciences||Co-Principal Investigator|
|Copley, Nancy||Woods Hole Oceanographic Institution (WHOI BCO-DMO)||BCO-DMO Data Manager|
Estimates of per capita sea urchin grazing rates on Clathromorphum nereostratum, evaluated as a function of sea urchin size. Assays were performed under ambient conditions in a controlled mesocosm setting, using the urchin Strongylocentrotus polyacanthus.
We conducted a controlled laboratory experiment to test whether the capacity of S. polyacanthus to consume C. nereostratum scales with its size. Conducted under ambient light and continuous water flow (mean water temperature ~8.5 degrees C), this feeding experiment consisted of five sea urchin size classes (15-55 mm test diameter; binned in 10 mm size classes, n = 5/size class). Size classes were evenly distributed among blocks (n = 5), with each block including a control alga (i.e., C. nereostratum caged alone) to account for algal growth as well as loss due to factors other than herbivory (see calculation below). Urchins were individually housed with a single C. nereostratum colony. We assessed the blotted wet mass of each C. nereostratum at the beginning of the assay, then again after 10 days. We calculated the (corrected) amount of C. nereostratum consumed in each assay using the equation [Ti x (Cf/Ci)] - Tf, where Ti and Tf is the initial and final mass (respectively) of an alga exposed to herbivory and Ci and Cf is the initial and final mass (respectively) of its paired control.
After computing per capita grazing rate ("amount.mg.consumed/day") for each urchin, we also standardized each per capita grazing rate by the estimated biomass (calculated via a known size-weight relationship) of the individual urchin ("amount.mg.consumed/d/gram.urchin").
Finally, we quantified the maximum depth (mm) to which each urchin grazed C. nereostratum by examining each sample under a microscope and measuring the depth of the most significant grazing scar using an ocular micrometer.
BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
|treatment||target size class of sea urchin||millimeters|
|replicate||replicate individual urchin or alga||unitless|
|urchin_diameter_mm||actual size (test diameter) of sea urchin||millimeters|
|urchin_biomass_grams||biomass of sea urchin; estimated using known length-weight relationship||grams|
|cca_mass_initial_grams||initial mass of coralline alga||grams|
|cca_mass_final_grams||final mass of coralline alga||grams|
|correction_factor||correction factor; computed by dividing the final mass of the paired control alga by its initial mass (Cf/Ci)||unitless|
|corrected_cca_mass_initial_grams||cca_mass_initial_grams * correction_factor||grams|
|amount_grams_consumed||amount of coralline algae consumed: corrected_cca_mass_initial_grams minus cca_mass_final_grams||grams|
|amount_mg_consumed||amount of coralline algae consumed||millimeters|
|amount_mg_consumed_day||rate of algal consumption (per day)||millimeters|
|amount_mg_consumed_d_gram_urchin||rate of algal consumption (per day): standardized by the biomass of the individual sea urchin||millimeters|
|max_depth_grazed_mm||maximum depth of sea urchin grazing scar on the coralline alga||millimeters|